<!DOCTYPE html>
<html>
<head>
    <meta charset="UTF-8">
    <title>文档标题</title>
    <style>
        .father{
            border: 1px solid #f00;
            /* 1. 把父盒子设置成伸缩盒布局
                特征：子元素默认水平排列
            */
            display: flex;
            /* 2. flex方向 */
            flex-direction: column ;
        }
        .son{
            width: 100px;
            height: 100px;
            background-color: pink;
            border:1px solid deepskyblue;
        }
    </style>
</head>
<body>
    <div class="father">
        <div class="son">1</div>
        <div class="son">2</div>
        <div class="son">3</div>
        <span>行内</span>
        <span>行内</span>
    </div>
</body>
</html>